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Marco Elver authored
In the kernel, the "volatile" keyword is used in various concurrent contexts, whether in low-level synchronization primitives or for legacy reasons. If supported by the compiler, it will be assumed that aligned volatile accesses up to sizeof(long long) (matching compiletime_assert_rwonce_type()) are atomic. Recent versions of Clang [1] (GCC tentative [2]) can instrument volatile accesses differently. Add the option (required) to enable the instrumentation, and provide the necessary runtime functions. None of the updated compilers are widely available yet (Clang 11 will be the first release to support the feature). [1] https://github.com/llvm/llvm-project/commit/5a2c31116f412c3b6888be361137efd705e05814 [2] https://gcc.gnu.org/pipermail/gcc-patches/2020-April/544452.html This change allows removing of any explicit checks in primitives such as READ_ONCE() and WRITE_ONCE(). [ bp: Massage commit message a bit. ] Signed-off-by:
Marco Elver <elver@google.com> Signed-off-by:
Borislav Petkov <bp@suse.de> Signed-off-by:
Thomas Gleixner <tglx@linutronix.de> Acked-by:
Will Deacon <will@kernel.org> Acked-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200521142047.169334-4-elver@google.com
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